Iron studies pair
Ferritin and TIBC (total iron binding capacity): how to read them together
Ferritin and TIBC are interpreted together because ferritin can be misleadingly normal or even raised during inflammation, while TIBC moves in the opposite direction during true iron deficiency.
Quick answer
Ferritin and TIBC (total iron binding capacity) are interpreted together because ferritin and TIBC are interpreted together because ferritin can be misleadingly normal or even raised during inflammation, while TIBC moves in the opposite direction during true iron deficiency. UK reference: NICE CKS Anaemia (iron deficiency, August 2024 revision).
Why these markers are ordered together
Ferritin is the stored form of iron and a sensitive marker of true iron deficiency, but it is also an acute-phase protein, meaning it rises during infection, inflammation, malignancy and liver disease. TIBC (total iron binding capacity) measures the binding capacity of transferrin, the protein that transports iron in blood. In iron deficiency, the body upregulates transferrin production to capture every available iron molecule, so TIBC rises while ferritin falls. Reading the two together resolves the ambiguity ferritin alone creates.
Four scenarios, four interpretations
The 2x2 interpretation matrix our clinicians use when these markers come back together.
Low ferritin (under 30 ug/L) + High TIBC (over 70 umol/L)
What it likely means: True iron deficiency. The classic pattern, with no contradicting signals.
What to do next: Iron replacement (oral ferrous sulphate, ferrous fumarate or ferrous gluconate per NICE CKS Anaemia), repeat ferritin in 3 months. Investigate the cause of the deficiency (menstrual loss, dietary, GI loss). Post-menopausal women and men with iron deficiency need GI investigation.
Low ferritin + Normal or Low TIBC
What it likely means: Iron deficiency masked by inflammation. The inflammatory response suppresses TIBC even when iron is genuinely low.
What to do next: CRP and ESR to confirm the inflammatory context. If raised, identify the source of inflammation (subclinical infection, autoimmune disease, malignancy). Iron deficiency may still be present and treatable, but cause matters.
High ferritin + Normal TIBC
What it likely means: Acute-phase ferritin rise (most common), liver disease, chronic alcohol use, or metabolic syndrome. NOT iron overload.
What to do next: CRP first to confirm acute-phase context. Liver function tests if alcohol or hepatitis is suspected. Repeat ferritin in 4-6 weeks after any acute illness resolves.
High ferritin + Low TIBC + High transferrin saturation
What it likely means: True iron overload, investigate for hereditary haemochromatosis (HFE gene), iron-loading anaemias, or transfusion-related overload.
What to do next: Transferrin saturation calculation and HFE genetic testing per BSH 2018 hereditary haemochromatosis guideline. Refer to haematology.
When the pair is ambiguous
During or shortly after acute illness, ferritin is unreliable. Repeat both markers 4-6 weeks after recovery for an honest baseline. In chronic inflammation, soluble transferrin receptor (sTfR) can clarify true iron status independently of acute-phase changes.
Individual markers
Read about each marker in isolation:
Get the pair tested together
Both markers in one blood draw at 134 Harley Street. Custom panels designed by a GMC-registered doctor from £275, or fixed panels including this pair from £249.